Source Configuration Research Articles

NUMERICAL ANALYSIS OF BOREHOLE HEAT EXCHANGER PERFORMANCE IN SHALLOW GRAVEL AQUIFERS AND CLAY-DOMINATED SOIL

The performance of geothermal heat extraction in shallow aquifers depends on both Borehole Heat Exchanger (BHE) and soil or aquifer properties. In this work, an analysis of the thermal yield of a shallow geothermal reservoir was made numerically with the finite element method used to simulate heat and mass transfer in the three-dimensional reservoir. The main parameters for analysis which have been considered are the geometry and physical parameters of the BHE and grout, as well as aquifer matrix and groundwater fluid. Physical parameters are thermal conductivity, flow conductivity, expansion coefficient, porosity, volumetric heat capacity, anisotropy and dispersivity. The numerical tests have been performed in single BHE line source configuration representing numerically modelled thermal response test for the estimation of sustainable heat extraction. The domain size was a 100x100 meter rectangle with a depth of 200 meters. Three main lithological configurations have been modelled: gravel aquifer with low and high convection of groundwater fluid, as well as a shallow geothermal reservoir dominated by clay material without convection. For selected cases, the analysis for temporal and spatial discretization was also made. Three-dimensional transient modelling was made in FEFLOW® software with pre- and post-processing done in user-defined Python scripts. The results show the most influential parameters to be considered when setting up the real case simulation of geothermal heating and cooling, as well as optimal temporal and spatial discretization set-up with respect to expected thermal gradients in the reservoir.

Secondary source reconfiguration for a Westinghouse four-loop plant

An approach is described for estimating the excore source range detector count rate for several secondary neutron source configurations. A case in which a Westinghouse four-loop plant considered relocating the secondary source fuel assemblies and switching from secondary source fuel assemblies with six secondary source rods to assemblies with two or four secondary source rods is presented. The excore detector count rate is first estimated computationally, by modeling the secondary source fuel assemblies and excore detectors in MCNP and predicting the detector count rate based on detector sensitivity in cps/nv listed in the detector manual. Since the excore detector response can vary greatly from cycle to cycle even for equilibrium loading patterns due to variations in detector response, benchmarking to actual excore source range detector count rates is presented. A correction factor for each individual source range detector is determined from the benchmark, then applied in the prediction of excore source range detector count rate for the proposed two or four secondary source rod configurations. The approach presented in this paper could also be used to perform an engineering evaluation on the feasibility of elimination of secondary sources.

Electrophysiological brain imaging based on simulation-driven deep learning in the context of epilepsy

Identifying the location, the spatial extent and the electrical activity of distributed brain sources in the context of epilepsy through ElectroEncephaloGraphy (EEG) recordings is a challenging task because of the highly ill-posed nature of the underlying Electrophysiological Source Imaging (ESI) problem. To guarantee a unique solution, most existing ESI methods pay more attention to solve this inverse problem by imposing physiological constraints. This paper proposes an efficient ESI approach based on simulation-driven deep learning. Epileptic High-resolution 256-channels scalp EEG (Hr-EEG) signals are simulated in a realistic manner to train the proposed patient-specific model. More particularly, a computational neural mass model developed in our team is used to generate the temporal dynamics of the activity of each dipole while the forward problem is solved using a patient-specific three-shell realistic head model and the boundary element method. A Temporal Convolutional Network (TCN) is considered in the proposed model to capture local spatial patterns. To enable the model to observe the EEG signals from different scale levels, the multi-scale strategy is leveraged to capture the overall features and fine-grain features by adjusting the convolutional kernel size. Then, the Long Short-Term Memory (LSTM) is used to extract temporal dependencies among the computed spatial features. The performance of the proposed method is evaluated through three different scenarios of realistic synthetic interictal Hr-EEG data as well as on real interictal Hr-EEG data acquired in three patients with drug-resistant partial epilepsy, during their presurgical evaluation. A performance comparison study is also conducted with two other deep learning-based methods and four classical ESI techniques. The proposed model achieved a Dipole Localization Error (DLE) of 1.39 and Normalized Hamming Distance (NHD) of 0.28 in the case of one patch with SNR of 10 dB. In the case of two uncorrelated patches with an SNR of 10 dB, obtained DLE and NHD were respectively 1.50 and 0.28. Even in the more challenging scenario of two correlated patches with an SNR of 10 dB, the proposed approach still achieved a DLE of 3.74 and an NHD of 0.43. The results obtained on simulated data demonstrate that the proposed method outperforms the existing methods for different signal-to-noise and source configurations. The good behavior of the proposed method is also confirmed on real interictal EEG data. The robustness with respect to noise makes it a promising and alternative tool to localize epileptic brain areas and to reconstruct their electrical activities from EEG signals.

Energy, Exergy and Thermoeconomic Analyses on Hydrogen Production Systems Using High-Temperature Gas-Cooled and Water-Cooled Nuclear Reactors

The use of nuclear energy is inevitable to reduce the dependence on fossil fuels in the energy sector. High-temperature gas-cooled reactors (HTGRs) are considered as a system suitable for the purpose of reducing the use of fossil fuels. Furthermore, eco-friendly mass production of hydrogen is crucial because hydrogen is emerging as a next-generation energy carrier. The unit cost of hydrogen production by the levelized cost of energy (LCOE) method varies widely depending on the energy source and system configuration. In this study, energy, exergy, and thermoeconomic analyses were performed on the hydrogen production system using the HTGR and high-temperature water-cooled nuclear reactor (HTWR) to calculate reasonable unit cost of the hydrogen produced using a thermoeconomic method called modified production structure analysis (MOPSA). A flowsheet analysis was performed to confirm the energy conservation in each component. The electricity generated from the 600 MW HTGR system was used to produce 1.28 kmol/s of hydrogen by electrolysis to split hot water vapor. Meanwhile, 515 MW of heat from the 600 MW HTWR was used to produce 8.10 kmol/s of hydrogen through steam reforming, and 83.6 MW of electricity produced by the steam turbine was used for grid power. The estimated unit cost of hydrogen from HTGR is approximately USD 35.6/GJ with an initial investment cost of USD 2.6 billion. If the unit cost of natural gas is USD 10/GJ, and the carbon tax is USD 0.08/kg of carbon dioxide, the unit cost of hydrogen produced from HTWR is approximately USD 13.92/GJ with initial investment of USD 2.32 billion. The unit cost of the hydrogen produced in the scaled-down plant was also considered.

On groundwater flow and shallow geothermal potential: A surrogate model for regional scale analyses

Many cities worldwide lay upon alluvial aquifers which have a great potential for low temperature geothermal installations thanks to the thermal diffusive properties of saturated porous media and the constant temperature of the subsurface. In addition, aquifers with fast moving groundwater have a higher potential due to the additional energy replenishment by advection, which is often underestimated.This work aims at bridging the gap between quantitative hydro-thermal numerical analysis and regional scale assessment developing a process-based surrogate model for the estimation of the thermal exchange (geothermal) potential of ground source heat pumps (GSHP) considering groundwater advection. The proposed method is based on a synthetic 3D FEM model reproducing the infinite line source configuration and introducing groundwater advection. Conductive/advective g-functions were derived from the numerically simulated space-time thermal perturbation for a comprehensive set of hydrogeological regimes, and a surrogate model was developed by a machine learning (ML) regression of the thermal response of the system. This solution, beyond the run time of the numerical study and the ML training phase, is very fast, applicable at any scale and scalable to any desired depth.The trained model can be used to predict the geothermal potential of GSHP for almost all sedimentary basins around the world upon the availability of the required input data (aquifer thickness and saturation, aquifer porosity and groundwater flow velocity). In this study, large scale geothermal potential maps were generated from input layers implemented in a GIS, for a demonstrative area in northern Italy showing highly variable groundwater flow (Darcy velocity from 10−3 to 10+3 m/y). A promising increase (up to +250 %) in the thermal exchange potential of GSHP due to the contribution of advection was highlighted discussing the benefits of groundwater flow and the amount of usable potential with implications on shallow geothermal energy management and development.

A Systematic Tri-level Demand-driven Supply-side Management Approach on Enhancing Building Energy Performance in an Educational Institution

The concept of demand-side management (DSM) is a ceaseless research topic craving an advanced, superior, and qualitative strategy for improving customers’ level of satisfaction with energy utilization. It encourages the active participation of prosumers and paves the way for sufficient energy proficiency. However, less attention is paid to accounting for consumers’ comfort and priorities. This paper presents a tri-level systematic approach for implementing demand-side and supply-side management at the consumer end. The proposed Tri-level Demand-Driven Supply-Side Management (TDD-SSM) framework commences with gathering knowledge on available loads in the department building block of a higher educational institution situated in the Madurai district of Tamil Nadu, India. The incorporated DSM technique follows strategic load categorization and load scheduling. Following that, a feasibility study on optimal sources is accomplished with Hybrid Optimization of Multiple Energy Resources software. The simulation is done to have a clear comparison in rendering a techno-enviro-economically feasible configuration of energy source to loads (with and without DSM). Ultimately, the framework concludes by picking the most promising energy configuration through the ideal computational multi-criteria decision-making–Preference Ranking Organization Method for Enrichment Evaluation II approach, which highlights the energy configuration of photovoltaic solar generation supply along with grid feeding loads after DSM incorporation and is found to be the best energy configuration under techno-enviro-economic criteria.

On the feasibility of using an autonomic control loop and automated planning for tenant-oriented reconfiguration of network slices

In 5G, 6G and beyond networks, tenants need capabilities to reconfigure network slices since they must react quickly to changing network conditions and end-users’ demands to meet Service Level Agreements. Offering reconfiguration operations to tenants is challenging since those functions must be autonomous and governed by high-level network management policies. Existing approaches face the network slice reconfiguration problem from the provider perspective, disregarding the importance of providing slice reconfiguration capabilities to tenants. This paper presents an approach called ATRAP to demonstrate the feasibility of using an autonomic control loop and automated planning for reconfiguring network slices from the tenant perspective. ATRAP introduces a tenant-oriented architecture based on the monitor-analyze-plan-execute-knowledge method and automated planning for computing reconfiguration plans autonomously. An ATRAP’s plan aims to turn a network from a source configuration where one or more intents representing high-level network management policies are unmet into a target configuration in which the network meets the intents again. As ATRAP represents a network slice as a Service Function Chain comprising Virtual Network Functions (VNFs) and virtual links connecting them, a reconfiguration plan involves tasks to migrate VNFs and virtual links into the substrate network in a particular order. Results revealed as ATRAP computes plans with few migrations of VNFs and their adjacent links, leading to low reconfiguration costs related to short service disruptions. Also, results showed as ATRAP’s planning time depends on the size of the substrate network and the tenant’s slices. The results evidence that ATRAP is an attractive and feasible solution for the in-tenant reconfiguration of network slices.

Localising and identifying radionuclides via energy-resolved angular photon responses

A technique for the in-situ localisation of radioactivity is described whereby the energy-resolved angular photon response of a collimated inorganic scintillation detector is used to derive the spatial arrangement of a variety of radioactive source configurations. The influence of photon radiation (X- and γ ray) incident on the collimated detector is expressed mathematically, by way of a sinc transform embedded to a dynamic linear regression model, to increase the spatial accuracy of the localisation. This approach is tested experimentally with two pairs of like radionuclides, two pairs of different combinations of radionuclides and three different radionuclides to demonstrate its combined isotopic discrimination and spatial localisation capabilities. A fit based on the model referred to above is observed to reproduce the data for the combined X- and γ-ray regions of interest effectively. This allows for increased resolution via interpolation between the data which is observed to improve location accuracy significantly. This research is relevant to applications in autonomous robotic exploration tasks and for the characterisation of contaminated environments associated with nuclear legacies and radiological emergencies.

Characterization of a circular arc electron source for a self-neutralizing air-breathing plasma thruster

The paper presents an enhanced version of an arc electron source designed for air ionization applications in a self-neutralizing air-breathing plasma thruster. The arc electron source is specifically suited for the air-breathing plasma thruster, as it allows precise control of mean electron energy levels. This paper focuses on the ionization aspects of air-breathing thrusters through the development of axially magnetized arc electron sources. The sources consist of a circular and coaxial configuration of a metallic arc plasma source coupled with a positively biased grid to extract electrons and control mean electron energy. The average mean electron energy of electrons in the arc electron source is regulated by adjusting the bias voltage of the grid within the range of 0 V – 300 V. To investigate the behavior of ion current density and electron density concerning pressure and mean electron energy, the current probe and magnetic filter were utilized. It was demonstrated that the circular electron source leads to enhanced ionization of airflow by achieving plasma densities greater than 1018 m−3. By utilizing a high-speed camera for the circular arc electron source, the arc spot was seen to move azimuthally due to the magnetic field. Furthermore, scanning electron microscopy and a conductance measurement system were employed for the coaxial arc electron source to examine the deposition and conductance of the electron extraction grid. While the grid underwent deposition of about 600 microns, the conductance was observed to increase/saturate with time and bias voltage, indicating an electrically “self-healing material”.

A Methodology for Predicting Improved Dipole Source Configurations From Near-Field Scan Data

Equivalent sources found from near-electric and magnetic field scans are often used to predict and solve interference problems. While there are many ways to represent the source, the user lacks the ability to determine which of the many possible source configurations is more likely to represent the “true” source, and thus accurately represent field data outside the measurement area and in the presence of typical measurement errors. A methodology is proposed for estimating which of many possible dipole source representations of near-field scan data are likely to give better estimates of fields outside the measurement scan plane when utilizing imperfect measurement data. A quality metric for determining better configurations is proposed, which utilizes the statistical variation of the global difference measure (GDM) in the predicted and measured fields. Equivalent sources are estimated when adding noise to measurement data, and prediction statistics are generated for multiple instantiations of measured noise. Results demonstrate that the better configurations minimize the average plus standard deviation of the GDM. The ability of the technique to identify robust source configurations was tested when measurements were subject to additive measurement noise, cross-field coupling, and systematic errors in probe position, and was evaluated based on its ability to predict fields at points above and to the side of the measurement plane. The method consistently identified better source configurations using both simulated and measured data.

Seismic Identification and Hydrocarbon Accumulation Characteristics of Submarine Fan in offshore Suriname

In recent years, oil and gas fields have been continuously discovered in the Suriname-Guyana Basin of South Atlantic, the reservoir of which is submarine turbidite sandstone and become one of the hot exploration objectives in the world. Based on the interpretation and analysis of 2D seismic and well data, this paper presents the integrated geological and geophysical evaluation of the Suriname-Guyana basin within Suriname and describes the identification characteristics and hydrocarbon accumulation process of submarine fan in offshore Suriname. The tectonic evolution of this region can be divided into four stages, breakup of Pangea, intracontinental rift, regional uplift and drifting over the South Atlantic. The Upper Cretaceous marks the transition of a transgressive to a regressive system with increasing sediment input from the south west, creating a broad delta plain environment across the shallow offshore area. It has been confirmed that multi-stage submarine fans have developed from Upper Cretaceous to Neogene in offshore Suriname, with overlapping characteristics of multiple erosive surfaces. It is suggested that erosive surface forming local unconformity is the important identification mark of submarine fan. Among them, the Paleogene and Upper Cretaceous submarine fans are the most widely distributed and have the most obvious characteristics on seismic profiles. The bottom of the Paleogene and Upper Cretaceous fans are identified by the erosive surfaces. The fan root has obvious characteristics of cutting valley, forming inter-bedded with the deep-sea facies toward the outer fan, along with litho-logic granularity thinning and scope expansion. The distal parts of the submarine fan are surrounded by abyssal shale, which can form a good source, reservoir and cap configuration. Therefore, turbidite fan sandstone with good source rock and cap configuration is the favorable reservoir.

Optimal Power Source Configuration of Independent Microgrid Based on Natural Resource Evaluation

Power source configuration is an important stage of independent microgrid planning, which guarantees the economic and reliable operation of the microgrid system. The type and capacity of power source for the independent microgrid are affected by the factors such as load level, geographical location, wind, solar, water, and other natural resources. This paper analyzed the characteristics of natural resources in different regions. The index evaluation system of wind, solar, and hydropower resource was constructed, and the fuzzy evaluation method was proposed to evaluate the wind-solar-hydropower resource. Considering the power supply reliability and environmental friendliness, the optimization model of the microgrid power source was established with the objective of minimum comprehensive generation cost and the power and energy balance as constraints. Generative Adversarial Networks (GANs) were applied to simulate the uncertainty of wind, solar, and hydropower output and generate multiple operation scenarios of independent microgrids. The improved method for the K-Medoids clustering algorithm was studied to reduce the number of operational scenarios and enhance computational efficiency. Finally, an example was presented to illustrate the analysis processes and verify the feasibility and rationality of the proposed method. The wind-solar-hydropower resource levels of 30 provinces in China were obtained, and five representative regions were selected. The power source configuration scheme of an independent microgrid in these regions was proposed, which provided a reference for independent microgrid planning.

Ensemble Forecasts of Solar Wind Connectivity to 1 Rs Using ADAPT‐WSA

AbstractThe solar wind which arrives at any location in the solar system is, in principle, relatable to the outflow of solar plasma from a single source location. This source location, itself usually being part of a larger coronal hole, is traceable to 1 RS along the Sun's magnetic field, in which the entire path from 1 RS to a location in the heliosphere is referred to as the solar wind connectivity. While not directly measurable, the connectivity between the near‐Earth solar wind is of particular importance to space weather. The solar wind solar source region can be obtained by leveraging near‐sun magnetic field models and a model of the interplanetary solar wind. In this article, we present a method for making an ensemble forecast of the connectivity presented as a probability distribution obtained from a weighted collection of individual forecasts from the combined Air Force Data Assimilative Photospheric Flux Transport‐Wang Sheeley Arge (ADAPT‐WSA) model. The ADAPT model derives the photospheric magnetic field from synchronic magnetogram data, using flux transport physics and ongoing data assimilation processes. The WSA model uses a coupled set of potential field type models to derive the coronal magnetic field, and an empirical relationship to derive the terminal solar wind speed observed at Earth. Our method produces an arbitrary 2D probability distribution capable of reflecting complex source configurations with minimal assumptions about the distribution structure, prepared in a computationally efficient manner.

A Novel Multi-Channel Tandem Applicator for Direction Modulated Brachytherapy

Intracavitary brachytherapy is a fundamental part of the treatment of cervical cancer that would be applied as boost therapy. However, the coverage of non-uniform targets is very challenging for this technique when dealing with the lateral extension of tumor, particularly when the tumor is too far superiorly to be covered by radiation dose from the ovoids or rings. In such situations, the conventional (single channel) tandem applicator would need to effectively provide the entire dose to the region yet have a very limited capacity for the intensity modulation due to the isotropic nature of radiation from the 192Ir HDR source. This limitation would require development of state-of-the-art interstitial-intercavitary applicators. In this study we aim to introduce a novel multi-channel tandem applicator design in alignment with the direction modulated brachytherapy (DMBT) concept to address this important issue. The novel multi-channel tandem applicator was designed using GEANT4 Monte Carlo simulations to consist of a base, made of MR compatible PEEK plastic, with a diameter of 6.5 mm and 19 channels each 1.1 mm in diameter, and in a honeycomb arrangement. The design also incorporated 18 iridium wires with a diameter of 0.9 mm that can actively enter the channels to provide intensity modulation at desired directions. A dosimetry study was then performed with different configurations of the 192Ir HDR source, also 0.9 mm in diameter, and up to 18 iridium wires inside the base. While offering the symmetrical dose distribution of the conventional tandem, the honeycomb design could produce a variety of directional dose distributions with different degree of extended lateral coverage. Additionally, this novel design with the configuration of 18 iridium wires inside the base covering the HDR source could reduce the radiation dose to approximately 15 % behind the shielded side at 1 cm from the tandem compared to the unshielded side. The results indicated that the honeycomb DMBT tandem design, as a noninvasive intracavitary approach, could be a promising solution for covering targets with lateral asymmetry/extension. Utilizing high-density material such as tungsten as the base material could reduce the radiation leakage through the base, improve the intensity modulation and hence lateral coverage.

Influence of Age on Speech Recognition in Noise and Hearing Effort in Listeners with Age-Related Hearing Loss.

The aim of this study was to measure how age affects the speech recognition threshold (SRT50) of the Oldenburg Sentence Test (OLSA) and the listening effort at the corresponding signal-to-noise ratio (SNRcut). The study also investigated the effect of the spatial configuration of sound sources and noise signals on SRT50 and SNRcut. To achieve this goal, the study used olnoise and icra5 noise presented from one or more spatial locations from the front and back. Ninety-nine participants with age-related hearing loss in the 18-80 years age range, specifically in the 18-30, 31-40, 41-50, 51-60, 61-70, and 71-80 age groups, participated in this study. Speech recognition and listening effort in noise were measured and compared between the different age groups, different spatial sound configurations and noise signals. Speech recognition in noise decreased with age and became significant from the age group of 50-51. The decrease in SRT50 with age was greater for icra5 noise than for olnoise. For all age groups, SRT50 and SNRcut were better for icra5 noise than for olnoise. The measured age-related reference data for SRT50 and SNRcut can be used in further studies in listeners with age-related hearing loss and hearing aid or implant users.

Dual ionization sources high-field asymmetric waveform ion mobility spectrometry with combined ultraviolet lamp source and corona discharge source

Dual ionization sources combining an ultraviolet (UV) lamp source and a corona discharge (CD) source were first used as ionization sources for high-field asymmetric waveform ion mobility spectrometry (FAIMS) to switch ionization modes without changing hardware. The CD source was manufactured using a tungsten needle and a copper ring and its usability was verified. The UV source and the CD source were combined into the FAIMS sensor and multiple ionization modes were attempted by controlling their on-off status. The optimal flow rate, quantitative and qualitative capabilities of the system were investigated, and the experiments on the impact of humidity and interferent on the system were conducted. The experimental results indicated that the flow rate of 3–4 L/min could ensure sufficient sensitivity and resolution of the system. The dual ionization sources configuration provided richer qualitative and quantitative information for FAIMS. This platform could operate in three ionization modes and had the potential to expand the analyzable compounds of UV-FAIMS. In summary, the research demonstrates that the dual ionization sources could be used as ionization sources for FAIMS, and the combined system provided convenience for chemical analysis.

Improving and warning the static stability limit of complex power grid tie-line based on WAMS

In order to solve the technical problems of traditional power system classic formulas that are difficult to explain the static stability limit changes of power grid interconnection lines, as well as the difficulties in improving and warning the static stability limit power of interconnection lines, this paper provides a method for improving and warning the static stability limit of power grid interconnection lines. Firstly, based on the electrical quantities measured by the wide-area measurement system (WAMS) of the power grid, the equivalent reactance of the power grid interconnection lines, and the equivalent impedance from the high voltage side and medium voltage side of the three coil transformers on both sides of the interconnection line are determined. Secondly, under pre-set operation mode and constraint conditions, the configuration quantity and capacity of the dynamic reactive power sources on the medium voltage side of the three coil transformers on both sides of the interconnection line are determined. Finally, based on the determined configuration and pre-set operation mode of the dynamic reactive power sources on the medium voltage side of the three coil transformers on both sides of the interconnection line, the historical electrical quantities measured by WAMS. The static stability limit and static stability margin of the interconnection line are calculated, and warnings are provided.

A high boost switched capacitor multilevel inverter with reduced components

ABSTRACT Switched capacitor multilevel inverters (SCMLIs) became a popular DC-to-AC converter due to their unique features like self-capacitor voltage balancing and self-output voltage boosting abilities over conventional multilevel inverters in recent years. However, recently developed SCMLIs suffer from higher component counts, lower voltage boosting factors, higher total standing voltage, and the requirement of isolated DC sources for generating high-quality output voltage level waveform. These drawbacks make the inverter costly, complex, and bulky. To address these drawbacks of SCMLIs, a novel SCMLI is proposed in this paper. The proposed SCMLI can realise 17 output voltage levels with a higher boosting factor. In addition, the proposed SCMLI uses lower switches, driver circuits, capacitors, and diodes than similar SCMLIs. The proposed SCMLI also offers a cheaper cost function per output voltage level per boosting factor compared to others. A thorough description of the proposed inverter’s operating principle, voltage stress analysis, and capacitor selection procedure have been discussed. The proposed inverter’s cascaded form has been constructed and analysed for various DC source configurations. An extensive simulation study of 17-level SCMLI in MATLAB/Simulink platform and an experimental investigation on a 17-level laboratory prototype validate the proposed SCMLI’s merits and effectiveness.

Effects of the oxygen source configuration on the superconducting properties of internally-oxidized internal-Sn Nb3Sn wires

We successfully manufactured 12-filament rod-in-tube Nb3Sn wires with oxide nanoparticles formed by the internal oxidation method. We employed Nb-7.5 wt%Ta-1 wt%Zr and Nb-7.5 wt%Ta-2 wt% Hf alloys along with oxygen sources (OSs) in two different configurations—in the core of Nb filaments (coreOS) and at the boundary between the filaments and the Cu tube (annularOS)—to assess the influence of the OS layout on the superconducting properties and grain size. The simultaneous presence of the OS and of Hf or Zr reduced the average Nb3Sn grain size to around 50 nm, leading to an enhancement of the layer critical current density (Jc ) up to 3000 A mm−2 at 4.2 K and 16 T for the Hf-annularOS wire. Samples manufactured with an OS show a shift toward higher reduced magnetic fields of the position of the maximum in pinning-force density, this shift being more pronounced when SnO2 is added in the annularOS configuration, and for the Hf-containing samples. This enhanced pinning at higher magnetic field is beneficial for high-field magnet applications. Moreover, we measured a very high upper critical field, reaching 29.3 T at 4.2 K in the Hf-annularOS samples.

A Suitable Magnetic Field Source Composed of an HTS Coil and HTS Bulks for Magnetic Drug Delivery System

To realize Magnetic Drug Delivery System (MDDS), it is necessary to reduce the frictional force on the inner surface of the blood vessel and increase the magnetic force in the longitudinal direction of the blood vessel acting on magnetic drugs deep inside the body. In other words, where the magnetic drugs are concentrated, the magnetic flux density gradient in the longitudinal direction of the blood vessel must be large and the magnetic flux density gradient perpendicular to the blood vessel surface must be small. However, creating such a magnetic field distribution with a single magnetic field source is difficult. Therefore, we investigated a magnetic field source configuration method that can increase the magnetic flux density gradient in the longitudinal direction of the blood vessel and decrease the magnetic flux density gradient perpendicular to the blood vessel surface by configuring the magnetic field source with an HTS coil and zero-field-cooled HTS bulks and using the antimagnetic effect of the HTS bulks. We examined the effect of the number of cylindrical HTS bulks on the magnetic force acting on the magnetic drugs. The shielding current field of the HTS bulk had the effect of reducing the magnetic flux density gradient perpendicular to the blood vessel surface and the relative position of the area where the magnetic drugs are concentrated and the shielding current region within the HTS bulk greatly affected the magnetic flux density gradient perpendicular to the blood vessel surface. Based on these results, we examined the effect of the distance between two cylindrical HTS bulks placed inside an HTS coil on the magnetic force acting on the magnetic drugs. The magnetic force in the longitudinal direction of the blood vessel was able to be increased by placing the HTS bulks so that the boundary of the HTS bulk (shielding current region) is near the area directly below the area where the magnetic drugs are concentrated. The distance between the square-column HTS bulks that maximized the magnetic force was longer than that of the cylindrical HTS bulks.